Vol 2016, No 9 (2016)

The decarbonization of breunnerite from talc waste is analyzed by thermogravimetry. The temperatures of thermal effects are determined, and kinetic models for the process are proposed to describe the mechanism of breunnerite decomposition. The unit cell parameters of breunnerite (Mg_xFe_1–x)CO₃ and the product of its decomposition, iron–magnesium oxide (Mg,Fe)O, are calculated. The apparent activation energies E_a of the decomposition are calculated using the Ozawa–Flynn–Wall and Kissenger model-free methods and the Avrami–Erofeev one-step model. Depending on the chosen model, the values of E_a range within 180–185 kJ/mol. The conditions of breunnerite roasting for the subsequent use of the obtained material in metallurgical processes are substantiated.

A set of studies, tests, and technological works is performed to design promising high-strength vessel steels for reactors with supercritical coolant parameters. Compositions and technological parameters are proposed for the production of reference steel (within the limits of the grade composition of 15Kh2NMFA-A steel) and high-nickel steel. These steels are characterized by high properties, including metallurgical quality and service and technological parameters. Steel of the reference composition has high (higher by 15%) strength properties, improved viscoplastic properties, and ductile–brittle transition temperature t_c of at most–125°C. The strength properties of the high-nickel steel are higher than those of the existing steels by 40–50% and higher than those of advanced foreign steels by 15–20% at ductile–brittle transition temperature t_c of at most–165°C. Moreover, the designed steels are characterized by a low content of harmful impurity elements and nonmetallic inclusions, a fine-grained structure, and a low susceptibility to thermal embrittlement.

The study of the electrochemical behavior of a soft magnetic amorphous Fe–P–Mo alloy in a 0.1M Na₂SO₄ solution, which simulates a damp SO₂-contaminated atmosphere, shows that the corrosion resistance of the nanocrystalline Fe_80.2P_17.1Mo_2.7 alloy is comparable to that of a FINEMET alloy. No molybdenum is required for manufacturing the Fe_80.2P_17.1Mo_2.7 alloy, because it can be prepared using natural alloy ferrophosphorus containing molybdenum.

The oxygen solubility in liquid nickel containing zirconium is studied experimentally for the first time at 1873 K. The equilibrium constants of the reaction of interaction between zirconium and oxygen dissolved in liquid nickel, the interaction parameters characterizing these solutions, and the zirconium activity coefficient in nickel at infinite dilution are found. The equilibrium constants of the reaction of interaction between zirconium and oxygen dissolved in the melt, the Gibbs energy of the reaction of interaction between zirconium and oxygen, and the interaction parameters characterizing these solutions are calculated at 1873 K for a wide composition range of Ni–Fe alloys. The oxygen solubility in various Ni–Fe melts containing zirconium is found at 1873 K. The deoxidizing capacity of zirconium increases as the iron content increases to 30% and decreases at higher iron content in the melt. This can be explained by the fact that an increase in the iron content lead to, on the one hand, a strengthening of the bonding forces of oxygen atoms in a melt and, on the other hand, to a significant weakening of the bonding forces of zirconium atoms with the base metal.

The influence of preliminary deformation upon rolling of wedge specimens on the mechanical properties and the structural phase state of Al–Cu–Li alloys are studied by X-ray diffraction and hardness measurements. Strong dependence of the hardening effect upon aging on the reduction upon rolling has been revealed. Deformation weakly influences the hardness and significantly increases the hardening upon aging. Herewith, the hardening effect is nearly absent at the minimum deformation ratio of 1% and increases with its increase. It is demonstrated that the content of T₁ phase increases from 2 to 4% in the range of a preliminary deformation ratio of 6–10% and the content of δ' phase is ~17% at a deformation ratio in the range 1‒6% and increases to 18–19% at a deformation ratio of 6–10%. The δ' phase in an alloy contains <20% nanocrystalline particles with 6–20 nm in size, and the remaining part consists of amorphous particles (as detected by X-ray diffraction) <5 nm in size, which precipitate coherently from the matrix and have the same orientation as the nanocrystalline particles and the solid solution.

The conditions of formation of hardened Cu–Zr–O alloys are determined theoretically and experimentally. Thermodynamic analysis of the possibility of formation of zirconium oxide in a liquid metal is performed by constructing the surface of component solubility in a metal melt. Disperse zirconium oxide inclusions in samples are detected by scanning electron microscopy and electron-probe microanalysis. The hardness and the electrical conductivity of experimental samples are measured in the as-cast state and after cold deformation. Hardness HV 133 is reached in cold-deformed samples containing 0.05 wt % Zr without heat treatment. The results obtained can be used to create a process for the formation of bulk composite materials based on copper and copper alloys.

The degassing from a hydrogen-saturated E125 zirconium alloy is studied as a function of its deformation. Zirconium alloy samples are subjected to tension at a relative elongation of 2.5, 5, and 10%. Undeformed and deformed samples were saturated with hydrogen by a galvanic method at a current density of 0.5 A/cm²; that is, they are hydrogen saturated and then deformed. As a result, the defects at which hydrogen is trapped in zirconium are identified. The quantity of hydrogen trapped by defects depends on the strain and the sequence of deformation and hydrogen saturation. This is a technical result of the investigations, which can be used to find optimum operation conditions for hydrogen-saturated zirconium articles.

It is experimentally shown that the metallic dust after the inertial explosion induced by the impact of a metallic bismuth striker on a fixed steel barrier contains platinum and boron, which were absent before the explosion. The existence of platinum and boron is qualitatively determined. The emission of single 8-MeV α particles is also detected from the metallic dust that forms at the site of the impact interaction of bismuth with steel. Both effects point to possible nuclear decay of bismuth due to the energy of a mechanical impact.